Help with Lens Reassembly

About a month back, I took apart a 135mm f/2 Nikkor for service(gummed solid focus) and stupidly did not mark the helical where it separated.

 

Now, I'm stuck with a lens I can't seem to get back together. Fortunately, I DO have the lower part of the focus aligned correctly, but I can't seem to get the helical started. If I have the bottom part set up correctly, there are plenty of clues as to the alignment, but still I'm stuck as to even get it started.

 

Can anyone give me some suggestions as to how I can approach putting these back together?

BTW, if it's of any relevance this is the AI-S version.

Reminds me of the time I took a Luger apart as a teenager.....:)

Sandy,

 

At least you didn't take a loaded one apart by accident on the firing line :)

 

When a good friend of mine first got his, he kept inadvertently hitting the take down lever when he would shoot it.

Multiple start threads are a real PIA to get started. You just have to keep trying.

As above! You just keep trying, using minimum (zero) force and trying to keep things perfectly square. If you mess up the entry surfaces, it may never to together again. It's a Zen thing. Then it will be wrong, but that's a clue as to where the next attempt should be made.

As above! You just keep trying, using minimum (zero) force and trying to keep things perfectly square. If you mess up the entry surfaces, it may never to together again. It's a Zen thing. Then it will be wrong, but that's a clue as to where the next attempt should be made.

 

Thanks-I'll do just that.

 

BTW, I saw you mention some silicone greases in a different thread and dismiss my use of silicone di-electric grease.

 

I know you mentioned some Dow products-any thoughts on Dow-Corning High Vacuum grease? It seems uncomfortably viscous for me, but I can easily get it which of course has an obvious advantage. I HAVE used it in the past to lubricate piston filler fountain pens and it does work fine in that application. Most recently, I used it on an older Mont Blanc, and it not only stopped a leak around the piston seal but also made a night and day difference in how the filler operated.

The best tip I can give for multi-start threads is to start backwards, unscrewing it. What you do is slowly & carefully mate up the ends of the threads, then being careful to keep alignment feel for the "drop" as the threads just engage, then reverse & start gently screwing in.

It is just a trial and error game. The trick is to ensure the two tubes are absolutely parallel to each other and the ends flat on.

 

An unscrewing motion might help, as you can feel the catch of the threads before trying to engage them.

 

Also check the thread ends for damage or dust/fibres sticking to them. Either will cause a bind and damage. A little extra lube rubbed round the start of the helicoid doesn't go amiss. (Neither does a quick scratched alignment mark before disassembly!):oops:

 

I have not had good experiences with silicone greases on dural. The silicone appears to attack any anodising. I use a good quality automotive lithium-based grease. I ran a separation/creep test on it and it stays intact really well.

Edited August 20, 2017 by rodeo_joe|1

I use a good quality automotive lithium-based grease. I ran a separation/creep test on it and it stays intact really well.

 

Any specific suggestions on brands/type/color?

 

I keep plenty of grease on hand, but my grease gun is loaded with Mobil 1 brand blue lithium. I also keep a couple of different types of red on hand(including the infamous "mechanic's glue" Lucas Red'n Tacky) and even some generic lithium grease with about the color of vaseline. I also have specialty greases like the "one tube lasts a couple lifetimes unbelievably expensive" Bosch distributor cam grease.

 

Since 1970s British steel likes to rust, I try to keep everything that could possibly do so on my MG appropriately oiled or greased :) .

I have an ancient can of Castrol grease. I can't be more specific than it's a medium viscosity brown automotive lithium-based bearing grease.

 

I'm sure it could be improved on, at great expense, for greasing helicoids. However, so far it's served me well with no sign of outgassing or creeping where it's not wanted.

 

Before using it, I placed a blob on a sheet of copy paper and baked it gently for a few hours. The oil ring around it was well contained, unlike some samples of medium viscosity silicone grease that spread much further.

Edited August 21, 2017 by rodeo_joe|1

I've been using something called "Lawson Super 77 Moly Grease" for this kind of thing for a long time. Its given me no problems yet, I just hope its still made!